A solar energy system includes a photovoltaic panel or a solar panel capable of generating direct current (DC) electric power when it is exposed to light. The solar panel has a positive-negative (PN) junction structure and has the characteristics similar to a PN junction diode. When photons hit the PN junction, the recombination of electrons and holes of the PN junction can result in an electrical current. However, the solar panel provides power depending on working environment such as optical density, weather, location, and temperature. Thus, the generated electric power may not be stable.